1. Field of the Invention
This invention relates to vehicular automatic and semi-automatic transmission systems providing a plurality of gear reduction ratios, such as automatic mechanical transmissions, and to control systems therefor. In particular, the present invention relates to control systems and methods for vehicles with throttle controlled engines and automatic or semi-automatic transmissions wherein gear selection and shift decisions are made and executed based upon measured and/or calculated parameters such as transmission output shaft or vehicle speed, transmission input shaft and/or engine speed, throttle position, calculated engine speed in a potentially engagable ratio, and the like. More particularly, the present invention relates to automatic/semi-automatic transmission control systems of the type described above having at least one mode of operation in which upshifting by more than a single ratio step will be commanded if conditions indicative of vehicle acceleration sufficient to indicate that single upshifting will result in a rapid requirement for further upshifting are sensed.
2. Description of the Prior Art
The use of automatic transmissions of both the automatic mechanical type utilizing positive clutches and of the planetary gear type utilizing frictional clutches is well known in the prior art as are control systems therefor. Electronic control systems for automatic transmissions wherein gear selection and shift decisions are made based upon certain measured and/or calculated parameters such as vehicle speed, engine speed, rate of change of vehicle speed, rate of change of engine speed, throttle position, rate of change of throttle position, full depression of the throttle (i.e. "kickdown"), actuation of the braking mechanism, currently engaged gear ratio, and the like are known in the prior art. Examples of such automatic transmission control systems for vehicles may be seen by reference to U.S. Pat. Nos. 4,722,248; 4,569,225; 4,595,986; 4,361,060; 4,073,203; 4,253,348; 4,038,889; 4,226,295; 3,776,048; 4,028,929; 4,039,061; 3,974,720 and 3,942,393, the disclosures of all of which hereby incorporated by reference.
Automated transmission systems having a selectable mode wherein skip downshifts, if allowable (i.e. engine speed in to be engaged ratio not greater than maximum allowable engine speed), assuming substantially constant vehicle speed, are selected are known in the prior art as may be seen by reference to U.S. Pat. No. 4,576,065, the disclosure of which is hereby incorporated by reference.
While the above referenced automatic transmission control systems, and similar systems, are effective to control an automatic transmission by selecting a desired gear ratio which will tend to optimize the fuel economy and/or performance of the vehicle in view of the sensed parameters and then to command a shift into the selected gear ratio, such control systems were not totally acceptable as the predetermined programs utilized to generate shift decision data, such as a shift pattern or patterns (also commonly referred to as a shift point profile) or the like did not optimize vehicle performance when vehicle acceleration (usually sensed as rotational acceleration of the transmission output shaft) sufficient to cause undesirably frequent single upshifting is sensed. If vehicle acceleration is such that, if only a single upshift is commanded, an additional upshift will be required in less than a reference period of time, vehicle performance will be unsatisfactory as the frequent shifting will be a nuisance and, in a mechanical transmission, the overly frequent torque interruptions during shift transients is inefficient.